The present invention relates to the field of containers for maintaining liquids and solid materials, such as food, at a substantially constant temperature over a relatively long period of time. One highly successful device for accomplishing this objective is a Dewar flask or Thermos bottle. A conventional Thermos bottle employs a double wall filler which may be made of metal, glass, plastic or other suitable material from which air is substantially evacuated.
In a first type of construction the double wall filler is formed in the shape of a cup and is provided with a protective liner on the inside so that in the event the vacuum filler breaks, the food or beverage in the liner will be protected from glass particles and the like. Additionally, the vacuum bottle is generally provided with an outside protective covering to prevent damage to the vacuum filler from accidental tipping, jostling and dropping.
A second type of vacuum thermos construction known in the art utilizes metal for the vacuum filler whereby the need for an outside protective casing is eliminated.
None of the above thermos constructions discloses a construction whereby a simple vacuum sleeve is utilized to form a vacuum insulating container. Such a construction has a number of advantages including lower cost, higher assembly rates and high thermal efficiency, and reduced resistance to breakage. U.S. Pat. No. 1,909,315 discloses a tubular vacuum sleeve through which a distillation column passes. However, there is no teaching of forming a vacuum insulated container nor does it show the use of a lining inside of the vacuum sleeve or disclose the use of a completely sealed and insulated base.
It is accordingly an object of the present invention to provide a vacuum insulated container which is low in cost and minimizes the number of forming operations.
It is another object of the present invention to provide a vacuum insulated container which has a high thermal efficiency.
It is another object of the present invention to produce a vacuum insulated container from a pair of concentric tubular members in which a liner for receiving food or beverage is provided and which has an insulated base at one end thereof and a removable closure at the other end thereof.
It is another object of the present invention to produce a vacuum insulated sleeve which can be utilized to form vacuum insulated containers of various opening configurations such as wide mouth or narrow mouth or convertible between wide and narrow mouth.
Other objects and advantages of the invention will be apparent from the concluding portion of the specification.